The invention relates to a tomograph for producing transverse layer images of a radiography subject, having a radiation measuring arrangement comprising a radiation source producing a fan-shaped radiation beam which penetrates the radiography subject, whose cross-sectional extent perpendicular to the layer plane equals the layer thickness and in the layer plane is so great that the entire radiography subject is penetrated, and also a radiation receiver which determines the intensity of radiation behind the subject, and also having a rotating device for the measuring arrangement for the purpose of irradiating the radiography subject from different directions, and having a measured value converter for transforming the signals supplied by the radiation receiver into a layer image, wherein the radiation receiver consists of a number of individual detectors.
There is known a tomograph of this type, where the radiation receiver consists of one single row of detectors. The number of detectors in the row of detectors is selected in accordance with the desired image resolution. The measuring arrangement is rotated through an angle of 360.degree. for the purpose of generating the input signals of the measured value converter. A tomograph of this description is suited as a so-called whole body scanner for the purpose of taking any desired transverse layer images of a patient. The length of the row of detectors must be dimensioned such that the x-ray beam detected by it completely penetrates each body layer to be reproduced.
The known tomograph has the disadvantage that when reproducing a body layer which is substantially smaller than the largest body layer, for example a cross section through the neck or the head of the patient, only a small number of detectors is active in producing the input signals of the measured value converter. The local resolution thus becomes smaller in relation to the size of the body layer to be reproduced.